sender login mismatch

Hi, just want some clarification on this server config setting.
I have the manual for 3.1 but there's no mention of it in there, dunno if it's been updated since I downloaded it.

if set, obviously it's supposed to block any email being sent if the sender address does not match the sasl authenticated address.
but what about any emails being sent from a domain alias or an email alias? do they get blocked as well?
if so, can they be made to work by adding them to the postfix config smtpd_sender_login_maps? and if so, do you have the correct entries to use for this?

ok. I've just tried it out on some test servers.
I thought it was all working fine with no config changes required, seemed to send ok for both an email alias, and a domain alias.

then I decided to try sending from an email alias configured in thunderbird, still authenticating with a real mailbox login, but without a matching alias configured in ispconfig. the email still got sent ok.
I wasn't expecting that. I guess if sasl_authentication gets passed, the user can send email as if it's from any address they want?